After deserting his forward operating base in Afghanistan in 2009, Sgt. Bowe Bergdhal left behind a note saying that he wanted to renounce his American citizenship, according to Fox News’ Jennifer Griffin.

Griffin said Tuesday on the Fox News Channel that she gathered this information through members of Bergdahl’s unit. She said the note was part of evidence being examined in the classified investigation on Sgt. Bergdahl’s behavior in theater.

Sgt. Bergdahl was exchanged for five senior Taliban commanders, many of whom are suspected of committing war crimes, slaughtering thousands of innocents, and collaborating with Al Qaeda.

On Tuesday, Chairman of the Joint Chiefs Martin Dempsey said that the Army was investigating the charges against Bergdahl, and “will not look away from misconduct if it occurred.”